金纳米线与亚波长狭缝结合实现局域场增强研究

为了获得更强的局域场来增强喇曼散射信号或非线性效应，提出了在亚波长金狭缝中放置两列紧邻金纳米线的结构，将两纳米线近场耦合效应和狭缝类法布里-珀罗共振对电场的放大作用结合起来实现纳米线间更强的电磁场.理论分析得出，两纳米线间电场强度在狭缝深度增加时呈现周期性起伏变化，满足类法布里-珀罗共振条件时出现峰值，且纳米线对于发生共振时狭缝深度有调制作用；电场强度在狭缝周期近似等于入射波长附近呈现突变趋势，在纳米线间距增加时呈指数递减.用有限元法对增强机理进行了仿真，结果表明：在纳米线间距为1 nm和2 nm时，增强效果较好；狭缝周期为600 nm、深度为310 nm、宽度为100 nm、纳米线间距为1 nm, 在波长650 nm时，两金纳米线中心热点处电场增强为200倍，达到109的喇曼增强因子，比单纯的两根金纳米线的热点处增强因子提高了3个数量级.

Abstract

In order to strengthen the electric field between two gold nanowires, a kind of structure was designed by putting them into periodical subwavelength slits. This structure combined the effect of amplifying electric field from the near-field coupled effect and the quasi-Fabry-Perot resonance. Theoretical study indicated that the electric field between gold nanowires showed periodical variation when depth of slits changes, and the peak of electric field appeared when Quasi-Fabry-Perot resonance happened, and nanowires were able to modulate the depth of resonance. The electric field turned out a sharp peak when the period was approaching to the wavelength of incident light, and it decreased rapidly as the interval of wires increased. According to the result calculated by finite element method, enhancing effect is considerable when the interval varies from 1 nm to 2 nm. It gets a 200 electric field enhancement which means a 109 Raman enhanced factor in hot spot between the two gold nanowires in subwavelength slits by reasonably adjusting the period and depth of the slits, which is three orders of magnitude than two lonely wires.

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宋超, 郝鹏, 余幕欣, 周文超, 陈思唯, 吴一辉. 金纳米线与亚波长狭缝结合实现局域场增强研究[J]. 光子学报, 2014, 43(1): 0116001_SC. SONG Chao, HAO Peng, YU Mu-xin, ZHOU Wen-chao, CHEN Si-wei, WU Yi-hui. Enhancing Electric Field with Gold Subwavelength Slits and Nanowires[J]. ACTA PHOTONICA SINICA, 2014, 43(1): 0116001_SC.

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